1. Technical Field
The present invention relates to voltage generation circuitry for a semiconductor apparatus.
2. Related Art
A semiconductor apparatus, specifically, a semiconductor memory apparatus, generates an internal voltage from an external voltage applied from an outside of the semiconductor memory apparatus and uses the internal voltage as a voltage supply source of internal circuits within a chip in order to perform a low power operation and a stable operation. In order to generate the internal voltage at an accurate level, a reference voltage serving as a reference for voltage generation is generated from the external voltage, and the internal voltage is generated using the reference voltage.
As described above, the reference voltage serves as a reference for generating the internal voltage. Accordingly, an external system inputs a generation code of plural bits (e.g., 6 bits) to the semiconductor apparatus, evaluates the characteristics of the semiconductor apparatus, which are represented by input parameters including Setup and Hold time, by changing the generation code from the minimum value to the maximum value, and decides a generation code representing optimal operation characteristics. An operation, in which the reference voltage is generated by changing the generation code from the minimum value to the maximum value and the generation code representing optimal operation characteristics is decided, is called reference voltage training. The generation code is inputted using plural bits of a mode register set signal in the case of a semiconductor apparatus such as a dynamic random access memory (DRAM).
However, the reference voltage generated in the semiconductor apparatus may deviate from a target value due to operation noise, coupling effect, power noise, and reduction in shielding force with peripheral lines. If the reference voltage generated in the semiconductor apparatus deviates from the target value, internal voltage value of the semiconductor apparatus may deviate from the target value, and operation characteristics may deteriorate. However, since an external system decides the generation code using the reference voltage training and fixes the generation code, it may be difficult to detect that the reference voltage deviates from the target value. Since the reference voltage is increasingly unstable with the development of a semiconductor apparatus, it is more difficult to generate a stable reference voltage